Video: Diver jumps from Nuuanu Reservoir spillway siphon when water is 60 feet lower than it was today. "Nu'uanu Reservoir was built between 1890-1910. Four reservoirs were built, one with a water tower (picture above) to control water levels."-- Venture Hawaii

So when the Nuuanu Reservoir this morning comes within five feet of cresting over the earthen banks and within 1.5 feet of being able to flow out of the spillway, the BWS and the Caldwell administration panic. 10,000 nearby residents are warned they may have to evacuate--then un-warned. Pumps and fire trucks are dispatched to the reservoir to draw down the water with fire hoses before it reaches the spillway.

Is this an indication that BWS and DLNR believe the dam cannot withstand a full load and that the existing spillway is too high to safely release water given what is apparently a weakened condition for the dam? Is something else wrong with the spillway?

The Board of Water Supply’s (BWS) Nu‘uanu Dam #1 is about a 1.5 feet below the spillway due to the amount of rain brought on by former Tropical Storm Olivia.

BWS has been monitoring and siphoning the excess water from the reservoir since the beginning of the week to keep the water level below the spillway. However, with the passing of Olivia, the rain exceeded the siphoning capacity. BWS and Honolulu Fire Department personnel are currently deployed at the dam with water pumps to bring the level of the reservoir down further.

BWS is working with the Mayor’s Office and the Department of Emergency Management to coordinate the operations plan, which includes public evacuation notification and sheltering if needed.

Approximately 10,000 residents would be affected. More information to come as it becomes available.

"In the very unlikely event that the dam should overflow and an evacuation be deemed necessary, here’s an image of the Nu’uanu Dam evacuation map. Water level is currently receding, and an evacuation is highly unlikely."